1. Field of the Invention
The present invention relates to an apparatus and method for separating and removing various components of a processing system which may adhere to one another. More particularly, the present invention provides a set of tapped holes and associated screws sized and adapted to facilitate separation and removal of the associated components.
2. Background of the Related Art
In the fabrication of integrated circuits, equipment has been developed to automate substrate processing by performing several sequences of processing steps without removing the substrate from a vacuum environment, thereby reducing transfer times and contamination of substrates. Such a system has been disclosed for example by Maydan et al., U.S. Pat. No. 4,951,601, in which a plurality of processing chambers are connected to a transfer chamber. A robot in a central transfer chamber passes substrates through slit valves in the various connected processing chambers and retrieves them after processing in the chambers is completed.
The processing steps carried out in the vacuum chambers typically require the deposition or etching of multiple metal, dielectric and semiconductor film layers on the surface of a substrate. Examples of such processes include chemical vapor deposition (CVD), physical vapor deposition (PVD), and etching processes.
It has been discovered that some processes perform better with, or even require, the heating of certain chamber components. For example, one organometallic compound of increasing interest as a material for use in ultra large scale integrated (ULSI) dynamic random access memory (DRAMS) is Barium Strontium Titanate (BST) due to its high dielectric constant. One manner of depositing BST is using a BST CVD process which entails atomizing a compound, vaporizing the atomized compound, depositing the vaporized compound on a heated substrate, and annealing the deposited film.
However, one difficulty encountered in a BST CVD process is that BST precursors have a narrow range of vaporization between decomposition at higher temperatures and condensation at lower temperatures, thereby requiring controlled temperatures from the vaporizer into the chamber and through the exhaust system. Accordingly, to prevent unwanted condensation on chamber components and to prevent decomposition, the internal surfaces of the chambers are preferably maintained at a suitable temperature above ambient (e.g., 200.degree. to 300.degree. C.).
Furthermore, it has been recognized that deposition layer uniformity can be enhanced and that system maintenance can be reduced, if substantially all of the system components (other than the substrate and the substrate heater) exposed to the process chemistry are substantially maintained at an ideal isothermal system temperature (e.g. 250.degree.+/-5.degree. C. for BST). Thus, the deposition chamber for such a process incorporates several active and passive thermal control systems.
Also, the BST deposition process may be performed at elevated substrate temperatures, preferably in the range of about 400.degree. to about 750.degree. C., and the annealing process may be performed at substrate temperatures in the range of about 550.degree. to about 850.degree. C. These high temperature requirements impose certain material property demands on the chambers used in the deposition process. For example, the elastomeric O-rings, typically used to seal the deposition chamber, are not generally made of materials that will resist temperatures in excess of about 100.degree. C. for many fabrication cycles. Seal failure may result in loss of chamber pressure as well as contamination of the process chemistry and system components resulting in defective film formation on the wafer. Therefore, the deposition chamber also includes thermal control features which serve to protect a main chamber seal by cooling the seal below the ideal isothermal system temperature.
However, the heating and cooling of the chamber components as well as the associated temperature differentials therebetween often can cause the components which must be removed and replaced to "stick" to one another. Likewise, other conditions, such as the close tolerances used in the manufacture of the chamber components, cause or contribute to the sticking of the components. Other factors that may contribute to sticking of components include mechanical clamping that often occurs when two flat plates are bolted together. The mechanical clamping combined with elevated temperatures may cause some fusing or inter-diffusion between the components. Also, the high vacuum environment of the process chambers further contributes to the sticking problem.
When maintenance of the chamber is required, the chamber is cooled and is at least partially disassembled by separating and removing some of the components. When the components are stuck together, however, the maintenance task becomes extremely burdensome because the components are relatively sensitive to damage and cannot merely be pried apart due to the precision with which the components are manufactured. Furthermore, prying would likely damage the plating, such as nickel plating, on the surfaces. Furthermore, because the components are manufactured with such close tolerances, prying apart the components is often impractical.
In some instances, a separating arrangement between the sticking pieces may be used, such as a threaded bore through a first component and a corresponding screw to separate the first component from a surface on a second component. To separate the first component from the second component, the screw is screwed into the threaded bore on the first component, and as the screw is threaded into the bore, the removal screw pushes against the surface to force the first component to separate from the surface of the second component. However, the screw may cause cosmetic surface damage on the second component and leave particles, such as nickel particles dislodged from the nickel plated surfaces, to contaminate the process. Also, threaded bores used to separate the components may be remotely located from threaded bores used to secure the components together, but in such instances, additional screws or plugs may be required if the second component cannot be exposed to the processing conditions. The additional holes and plugs and screws add undesirable complexity to the arrangement. Additionally, if the same holes used for attaching the components are used for removal and the removal screw pushes directly against the threaded bore surface, the threads in the threaded bore may be damaged, leading to further maintenance, repair, and increased likelihood of contaminant particles.
Consequently, there is a need for an apparatus and a method for separating the components of a processing chamber from the other components of the processing system to facilitate disassembly and maintenance of the system components without causing damage to either component.